Work vehicle and method of controlling work vehicle

ABSTRACT

A work vehicle includes: a vehicular body; a work implement having a boom pivotable with respect to the vehicular body, an arm pivotable with respect to the boom, and a bucket pivotable with respect to the arm; and a controller configured to calculate an angle of the bucket with respect to the arm according to an operation command before start of excavation, and control the work implement such that the calculated angle becomes equal to a first angle.

TECHNICAL FIELD

The present disclosure relates to a work vehicle.

BACKGROUND ART

A hydraulic excavator includes a work implement having a boom, an arm and a bucket. In the excavation operation of the hydraulic excavator including this work implement, an operator needs to move the operation levers for three axes corresponding to the boom, the arm and the bucket so as to control the movement of the bucket. For example, at the start of the excavation operation of the hydraulic excavator, the arm is operated to cause the bucket to dig into soil. When the operation of the arm is continued, the bucket deeply digs into soil, so that the resistance of soil is increased. Thus, an operation of manipulating the boom so as to raise the bucket is added. This achieves an appropriate depth of digging by the bucket with respect to the soil. Furthermore, after the arm and the bucket are operated such that a sufficient amount of soil is contained in the bucket, soil is raised, and the boom is further operated to move the bucket upward. Accordingly, it is not easy for the operator to perform an efficient excavation operation, and it is necessary for the operator to do some practice.

Conventionally, there has been a technique for automatically controlling the excavation operation for the purpose of performing an efficient excavation operation.

For example, Japanese Patent Laying-Open No. 61-225429 (PTL 1) discloses a system of detecting contact between a back surface of a bucket and an excavation surface in order to reduce the resistance of soil during the excavation operation, and automatically correcting the posture of the bucket in order to avoid interference of the back surface of the bucket.

Japanese Patent Laying-Open No. 62-189222 (PTL 2) discloses a system of measuring the weight of soil contained in a bucket to automatically adjust the depth of digging by the bucket such that the weight of the soil contained in the bucket becomes equal to the weight of the soil that is fully contained in the bucket.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laying-Open No. 61-225429

PTL 2: Japanese Patent Laying-Open No. 62-189222

SUMMARY OF INVENTION Technical Problem

In the excavation operation of the hydraulic excavator in each of the above-mentioned documents, various complicated computations may be required during the excavation operation, so that control may become complicated.

The present disclosure has been made to solve the above-described problems. An object of the present disclosure is to provide a work vehicle and a method of controlling the work vehicle, by which an efficient excavation operation can be performed in a simple manner without having to carry out a complicated computation during an excavation operation by adjusting the posture of a bucket before the start of excavation.

Solution to Problem

A work vehicle according to an aspect of the present disclosure includes: a vehicular body; a work implement including a boom pivotable with respect to the vehicular body, an arm pivotable with respect to the boom, and a bucket pivotable with respect to the arm; and a controller configured to calculate an angle of the bucket with respect to the arm according to an operation command before start of excavation, and control the work implement such that the calculated angle becomes equal to a first angle.

A method of controlling a work vehicle according to an aspect of the present disclosure is a method of controlling a work vehicle including a work implement that includes a boom pivotable with respect to a vehicular body, an arm pivotable with respect to the boom, and a bucket pivotable with respect to the arm. The method includes: receiving an operation command before start of excavation; calculating an angle of the bucket with respect to the arm according to the operation command; and controlling the work implement such that the calculated angle becomes equal to a first angle.

Advantageous Effects of Invention

According to the work vehicle and the method of controlling a work vehicle in the present disclosure, the posture of the bucket is adjusted before the start of excavation, thereby eliminating the need to carry out a complicated computation during the excavation operation, so that an efficient excavation operation can be performed in a simple manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an example of a work vehicle according to an embodiment.

FIG. 2 is a diagram schematically illustrating a work vehicle CM according to the embodiment.

FIG. 3 is a functional block diagram illustrating the configuration of a control system 200 configured to control work vehicle CM according to the embodiment.

FIG. 4 is a diagram illustrating the relation between the excavation angle of a bucket 8 and the resistance of soil according to the embodiment.

FIG. 5 is a diagram illustrating movement of work implement 2 in an excavation operation according to the embodiment.

FIG. 6 is a diagram illustrating the operation process of work vehicle CM in the excavation operation according to the embodiment.

FIG. 7 is a diagram illustrating the posture of bucket 8 according to the first modification of the embodiment.

FIG. 8 is a diagram illustrating the operation process of work vehicle CM in the excavation operation according to the first modification of the embodiment.

FIG. 9 is a functional block diagram illustrating the configuration of a control system 200A according to the second modification of the embodiment.

FIG. 10 is a diagram illustrating the operation process of work vehicle CM in the excavation operation according to the second modification of the embodiment.

FIG. 11 is a functional block diagram illustrating the configuration of a control system 200B configured to control a work vehicle according to another embodiment.

FIG. 12 is a diagram illustrating a concept of a work vehicle system according to another embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments according to the present disclosure will be hereinafter described with reference to the accompanying drawings. In the following description, the same components will be designated by the same reference characters. Names and functions thereof are also the same. Accordingly, the detailed description thereof will not be repeated.

[Entire Configuration of Work Vehicle]

FIG. 1 is a perspective view showing an example of a work vehicle according to an embodiment.

As shown in FIG. 1, a hydraulic excavator CM including a work implement 2 operated by hydraulic pressure will be hereinafter described by way of example as a work vehicle to which the concept of the present disclosure is applicable.

Hydraulic excavator CM includes a vehicular body 1 and a work implement 2.

Vehicular body 1 includes a revolving unit 3, an operator's cab 4 and a traveling unit 5.

Revolving unit 3 is disposed on traveling unit 5. Traveling unit 5 supports revolving unit 3. Revolving unit 3 is revolvable about a revolving axis AX. Operator's cab 4 is provided with an operator's seat 4S on which an operator sits. The operator who sits in operator's cab 4 operates hydraulic excavator CM. Traveling unit 5 has a pair of crawler belts 5Cr. Rotation of crawler belts 5Cr causes hydraulic excavator CM to travel. Traveling unit 5 may be formed of wheels (tires).

In the embodiment, the positional relation among components will be described with respect to the operator who sits on operator's seat 4S.

The front-rear direction means the front-rear direction with respect to the operator who sits on operator's seat 4S. The right-left direction means the right-left direction with respect to the operator who sits on operator's seat 4S. The right-left direction corresponds to the width direction of a vehicle (the vehicle width direction). The direction in which the operator sitting on operator's seat 4S faces forward is defined as a frontward direction. The direction opposite to frontward direction is defined as a rearward direction. The right side and the left side of the operator sitting on the operator's seat and facing forward are defined as a rightward direction and a leftward direction, respectively. The front-rear direction corresponds to an X-axis direction while the right-left direction corresponds to a Y-axis direction. The direction in which the operator sitting on operator's seat faces forward corresponds to the frontward direction (a +X direction). The direction opposite to the frontward direction corresponds to the rearward direction (a −X direction). When the operator sitting on operator's seat 4S faces forward, one direction of the vehicle width direction corresponds to the rightward direction (a +Z direction) while the other direction of the vehicle width direction corresponds to the leftward direction (a −Z direction).

Revolving unit 3 includes: an engine compartment 9 in which an engine is housed; and a counter weight provided in the rear portion of revolving unit 3. In revolving unit 3, a handrail 19 is provided frontward of engine compartment 9. An engine, a hydraulic pump and the like are disposed in engine compartment 9.

Work implement 2 is connected to revolving unit 3.

Work implement 2 includes a boom 6, an arm 7, a bucket 8, a boom cylinder 10, an arm cylinder 11, and a bucket cylinder 12.

Boom 6 is connected to revolving unit 3 through a boom pin 13. Arm 7 is connected to boom 6 through an arm pin 14. Bucket 8 is connected to arm 7 through a bucket pin 15. Boom cylinder 10 drives boom 6. Arm cylinder 11 drives arm 7. Bucket cylinder 12 drives bucket 8. The base end (the boom foot) of boom 6 and revolving unit 3 are connected. The leading end (the boom top) of boom 6 and the base end (the arm foot) of arm 7 are connected. The leading end (the arm top) of arm 7 and the base end of bucket 8 are connected. Each of boom cylinder 10, arm cylinder 11 and bucket cylinder 12 is a hydraulic cylinder driven by hydraulic oil.

Boom 6 is pivotable with respect to revolving unit 3 about boom pin 13 as a pivot shaft. Arm 7 is pivotable with respect to boom 6 about arm pin 14 as a pivot shaft extending in parallel to boom pin 13. Bucket 8 is pivotable with respect to arm 7 about bucket pin 15 as a pivot shaft extending in parallel to boom pin 13 and arm pin 14.

Each of boom pin 13, arm pin 14 and bucket pin 15 is in parallel to the Z-axis. Each of boom 6, arm 7 and bucket 8 is pivotable about the axis in parallel to the Z-axis.

FIG. 2 is a diagram schematically illustrating a work vehicle CM according to the embodiment.

As shown in FIG. 2, work vehicle CM is provided with a boom cylinder stroke sensor 16, an arm cylinder stroke sensor 17 and a bucket cylinder stroke sensor 18.

Boom cylinder stroke sensor 16 is disposed at boom cylinder 10 and configured to detect the stroke length (the boom cylinder length) of boom cylinder 10. Arm cylinder stroke sensor 17 is disposed at arm cylinder 11 and configured to detect the stroke length (the arm cylinder length) of arm cylinder 11. Bucket cylinder stroke sensor 18 is disposed at bucket cylinder 12 and configured to detect the stroke length (the bucket cylinder length) of bucket cylinder 12.

The stroke length of boom cylinder 10 will also be referred to as a boom cylinder length or a boom stroke. The stroke length of arm cylinder 11 will also be referred to as an arm cylinder length or an arm stroke. The stroke length of bucket cylinder 12 will also be referred to as a bucket cylinder length or a bucket stroke.

The boom cylinder length, the arm cylinder length and the bucket cylinder length will also be collectively referred to as cylinder length data.

Boom 6 has a length L1 corresponding to the distance between boom pin 13 and arm pin 14. Arm 7 has a length L2 corresponding to the distance between arm pin 14 and bucket pin 15. Bucket 8 has a length L3 corresponding to the distance between bucket pin 15 and a cutting edge 8 a of bucket 8. Bucket 8 has a plurality of blades. The leading end of bucket 8 will be referred to as cutting edge 8 a. Bucket 8 may not have a blade. The leading end of bucket 8 may be formed of a steel plate having a straight shape.

FIG. 2 shows vehicular body coordinate systems of an X-axis and a Y-axis with respect to boom pin 13 as a reference point (reference position).

Based on the cylinder length data detected by boom cylinder stroke sensor 16, an inclination angle θ1 of boom 6 with respect to the horizontal direction in the vehicular body coordinate systems is calculated. Inclination angle θ1 represents an angle formed between the horizontal line (X-axis) and the line segment that connects boom pin 13 and arm pin 14.

Based on the cylinder length data detected by arm cylinder stroke sensor 17, an inclination angle θ2 of arm 7 with respect to boom 6 is calculated. Inclination angle θ2 represents an angle formed between: the line segment that connects boom pin 13 and arm pin 14; and the line segment that connects arm pin 14 and bucket pin 15.

Based on the cylinder length data detected by bucket cylinder stroke sensor 18, an inclination angle θ3 of cutting edge 8 a provided in bucket 8 with respect to arm 7 is calculated. Inclination angle θ3 represents an angle formed between: the line segment that connects arm pin 14 and bucket pin 15; and the line segment that connects bucket pin 15 and cutting edge 8 a of bucket 8. Inclination angle θ3 will also be referred to as a bucket angle that represents an angle of bucket 8 with respect to arm 7.

As a method of calculating inclination angle θ, an explanation has been given with regard to a method of detecting the stroke length by using a stroke sensor to calculate inclination angle θ based on the detection result. However, the inclination angle may be calculated by using an angle detector such as a rotary encoder. The horizontal line (horizontal direction) is detected by an inertial measurement unit (not shown), but may be detected by an inclination sensor, an acceleration sensor and the like.

[Configuration of Hydraulic System]

FIG. 3 is a functional block diagram illustrating the configuration of a control system 200 configured to control work vehicle CM according to the embodiment.

As shown in FIG. 3, control system 200 according to the embodiment is configured to control the operation of excavation performed using work implement 2.

Control system 200 includes a boom cylinder stroke sensor 16, an arm cylinder stroke sensor 17, a bucket cylinder stroke sensor 18, an operation device 25, a work implement controller 26, a hydraulic cylinder 60, a direction control valve 64, and a pressure sensor 66.

Operation device 25 is disposed in operator's cab 4. Operation device 25 is operated by an operator. Operation device 25 receives an operation command from the operator for driving work implement 2. Operation device 25 is an operation device of a pilot hydraulic type.

Directional control valve 64 adjusts the amount of hydraulic oil supplied to hydraulic cylinder 60. Direction control valve 64 is operated by the supplied oil. The oil supplied to the hydraulic cylinder for actuating the hydraulic cylinder (boom cylinder 10, arm cylinder 11 and bucket cylinder 12) is also referred to as hydraulic oil. The oil supplied to direction control valve 64 for actuating direction control valve 64 is also referred to as pilot oil. The pressure of the pilot oil is also referred to as a pilot oil pressure.

The hydraulic oil and the pilot oil may be discharged from the same hydraulic pump. For example, a part of the hydraulic oil discharged from the hydraulic pump may be decompressed by a pressure reducing valve, and the decompressed hydraulic oil may be used as pilot oil. The hydraulic pump (a main hydraulic pump) for pumping out hydraulic oil is different from the hydraulic pump for pumping out pilot oil (a pilot hydraulic pump).

In FIG. 3, the pilot oil that is discharged from the main hydraulic pump and decompressed by the pressure reducing valve is supplied to operation device 25.

The pilot oil pressure is adjusted based on the amount of operation of operation device 25. Pressure sensor 66 is connected to operation device 25. Pressure sensor 66 detects the pilot oil pressure that is generated according to the lever operation of operation device 25, and outputs the detected pilot oil pressure to work implement controller 26.

In accordance with the pilot oil pressure detected by pressure sensor 66, work implement controller 26 drives direction control valve 64 through which the hydraulic oil to be supplied to hydraulic cylinder 60 (boom cylinder 10, arm cylinder 11 and bucket cylinder 12) flows.

Operation device 25 includes a first operation lever 25R, a second operation lever 25L, and an excavation button 25P. First operation lever 25R is disposed on the right side of operator's seat 4S. Second operation lever 25L is disposed on the left side of operator's seat 4S. For first operation lever 25R and second operation lever 25L, the forward-backward and the rightward-leftward operations correspond to operations along two axes.

Excavation button 25P is used by an operator for instructing start of the excavation operation. According to the instruction given from the operator by pressing excavation button 25P, work implement controller 26 controls the posture of work implement 2 for the excavation operation. Specifically, the bucket angle is adjusted to a prescribed angle (the first angle), which will be described later.

Boom 6 and bucket 8 are operated by first operation lever 25R.

The operation of first operation lever 25R in the front-rear direction corresponds to the operation of boom 6. Boom 6 is raised and lowered according to the operation in the front-rear direction. The lever operation is performed for operating boom 6.

The operation of first operation lever 25R in the right-left direction corresponds to the operation of bucket 8. The excavation motion and the opening motion of bucket 8 are performed according to the operation in the right-left direction. The lever operation is performed for operating bucket 8.

Arm 7 and revolving unit 3 are operated by second operation lever 25L.

The operation of second operation lever 25L in the front-rear direction corresponds to the operation of arm 7. Arm 7 is raised and lowered according to the operation in the front-rear direction. The lever operation is performed for operating arm 7.

The operation of second operation lever 25L in the right-left direction corresponds to revolution of revolving unit 3. Revolving unit 3 is revolved in the rightward direction and the leftward direction according to the operation in the right-left direction.

According to the amount of operation of first operation lever 25R (the amount of operation of the boom) with respect to the front-rear direction based on the detection result from pressure sensor 66, work implement controller 26 drives direction control valve 64 through which the hydraulic oil to be supplied to boom cylinder 10 for driving boom 6 flows.

According to the amount of operation of first operation lever 25R (the amount of operation of the bucket) with respect to the right-left direction based on the detection result from pressure sensor 66, work implement controller 26 drives direction control valve 64 through which the hydraulic oil to be supplied to bucket cylinder 12 for driving bucket 8 flows.

According to the amount of operation of second operation lever 25L (the amount of operation of the arm) with respect to the front-rear direction based on the detection result from pressure sensor 66, work implement controller 26 drives direction control valve 64 through which the hydraulic oil to be supplied to arm cylinder 11 for driving arm 7 flows.

According to the amount of operation of second operation lever 25L with respect to the right-left direction based on the detection result from pressure sensor 66, work implement controller 26 drives direction control valve 64 through which the hydraulic oil to be supplied to the hydraulic actuator for driving revolving unit 3 flows.

The operation of first operation lever 25R in the right-left direction may correspond to the operation of boom 6 while the operation of first operation lever 25R in the front-rear direction may correspond to the operation of bucket 8. Also, the operation of second operation lever 25L in the right-left direction may correspond to the operation of arm 7 while the operation of second operation lever 25L in the front-rear direction may correspond to the operation of revolving unit 3.

[Resistance of Soil]

FIG. 4 is a diagram illustrating the relation between the excavation angle of bucket 8 and the resistance of soil according to the embodiment.

As shown in FIG. 4, the excavation angle of bucket 8 close to 0° is shown as a limit angle.

The excavation angle represents an angle between the direction of cutting edge 8 a of bucket 8 and the excavation direction (traveling direction) of cutting edge 8 a when bucket 8 is moved. The excavation angle shows a positive value when the excavation direction of cutting edge 8 a is toward the opening of bucket 8 during movement of bucket 8 with respect to the direction of cutting edge 8 a of bucket 8. The excavation angle also shows a negative value when the excavation direction of cutting edge 8 a is opposite to the opening of bucket 8.

When the excavation angle of bucket 8 is smaller than the limit angle, the outer sheath or the back surface of bucket 8 is more pressed against soil, so that the value of the resistance of soil against bucket 8 suddenly rises.

In the case where the excavation angle of bucket 8 is a prescribed angle Q, the resistance of soil against bucket 8 shows a minimum value.

The limit angle and prescribed angle Q are merely by way of examples and can be set at different values depending on the configuration of bucket 8.

Work vehicle CM according to the embodiment performs an efficient excavation operation in a simple manner by performing the excavation operation at an excavation angle at which the value of the resistance of soil is relatively small. Specifically, work vehicle CM performs the excavation operation in such a manner that the excavation angle becomes equal to prescribed angle Q. The manner that the excavation angle becomes equal to prescribed angle Q does not mean that the excavation angle becomes completely equal to prescribed angle Q, but may also include the case where the excavation angle becomes equal to the approximate value of prescribed angle Q.

[Summary of Excavation Operation]

FIG. 5 is a diagram illustrating the movement of work implement 2 in the excavation operation according to the embodiment.

FIG. 5 shows the case where arm 7 is operated.

At the start of the excavation operation by work implement 2, arm 7 is operated to cause bucket 8 to dig into soil. In this case, when the angle of bucket 8 with respect to arm 7 is fixed, the excavation angle in the excavation operation performed by operating arm 7 is fixed.

For example, when a bucket angle P of bucket 8 with respect to arm 7 is set, the excavation operation can be performed at an excavation angle Q by operating arm 7.

Accordingly, in the embodiment, the angle of bucket 8 with respect to arm 7 is adjusted to bucket angle P before the start of excavation such that the excavation angle in the excavation operation performed by operating arm 7 becomes equal to an optimum excavation angle (angle Q). The term “before the start of excavation” means before the start of the initial (the first) excavation operation and before the start of the subsequent (the second and subsequent) excavation operations.

Specifically, work implement controller 26 calculates the angle of bucket 8 with respect to arm 7 according to the operation command before the start of excavation, and controls the work implement such that the calculated angle becomes equal to a prescribed angle (angle P).

By the process as described above, the resistance of soil against bucket 8 in the excavation operation performed by operating arm 7 is reduced. Thus, by reducing the resistance (load) of soil against bucket 8, an efficient excavation operation can be performed in a simple manner.

In the excavation operation of a conventional hydraulic excavator, an operator needs to move the operation levers for three axes corresponding to the boom, the arm and the bucket such that the excavation angle in the excavation operation has an optimum value before the start of excavation. Thus, the operation is not easily performed and needs to be practiced. However, by the operation command before the start of excavation according to the embodiment, the bucket angle of bucket 8 is controlled to be an optimum excavation angle for the excavation operation. Accordingly, an efficient excavation operation can be performed by a simple operation.

[Operation Process]

FIG. 6 is a diagram illustrating the operation process of work vehicle CM in the excavation operation according to the embodiment.

As shown in FIG. 6, work implement controller 26 determines whether an input by excavation button 25P has been received or not (step S2). Specifically, work implement controller 26 determines whether an instruction given by the operation of an operator pressing excavation button 25P has been received or not.

In step S2, when work implement controller 26 determines that an input by excavation button 25P has been received (YES in step S2), it calculates a bucket angle (step S4).

Specifically, based on the detection result from bucket cylinder stroke sensor 18, work implement controller 26 calculates an angle (bucket angle) θ3 of bucket 8 with respect to arm 7.

In step S2, when work implement controller 26 determines that no input by excavation button 25P has been received (NO in step S2), it maintains the state in step S2.

Then, work implement controller 26 adjusts bucket angle θ3 to bucket angle P (step S6). Work implement controller 26 drives direction control valve 64 such that bucket angle θ3 is set at bucket angle P, and adjusts the hydraulic oil that is to be supplied to bucket cylinder 12.

Then, the process ends.

When only arm 7 is operated, work implement controller 26 adjusts bucket angle θ3 to bucket angle P such that the excavation angle formed between the excavation direction of cutting edge 8 a of bucket 8 and the direction of cutting edge 8 a of bucket 8 becomes equal to prescribed angle Q.

The posture of bucket 8 is adjusted before the start of excavation, that is, before the start of the excavation operation. Automatic control is performed such that the excavation angle achieved by operating arm 7 for the posture of bucket 8 becomes an optimum angle. Thereby, the resistance (load) of soil against bucket 8 at the start of excavation is reduced. By adjusting the posture of bucket 8 before the start of excavation, a complicated computation does not have to be done during the excavation operation, so that an efficient excavation operation can be performed in a simple manner.

Since an efficient excavation operation with low load can be performed, the fuel efficiency of the work vehicle can be improved.

Since preparations for the excavation operation can be started according to the instruction given from the operator by pressing excavation button 25P, an efficient excavation operation that is excellent in usability can be simply performed in the sense that the operator's intention is reflected.

(First Modification)

A work vehicle according to the first modification of the embodiment controls bucket 8 according to another operation command, not according to the instruction given by the operation of the operator pressing excavation button 25P.

The work vehicle according to the first modification of the embodiment determines whether the posture of bucket 8 is in the soil ejecting state or not. Then, when the posture of bucket 8 is in the soil ejecting state, the work vehicle autonomously adjusts the angle of bucket 8.

Specifically, based on the angle of bucket 8 with respect to the horizontal line, the work vehicle determines whether the soil ejecting state occurs or not.

FIG. 7 is a diagram illustrating the posture of bucket 8 according to the first modification of the embodiment.

FIG. 7 shows the case where angle θ3 of bucket 8 with respect to arm 7 is 0.

The figure shows a bucket-horizontal line angle θb formed between the horizontal line and the line segment that connects bucket pin 15 as the center of rotation of bucket 8 and cutting edge 8 a of bucket 8, in the case where angle θ3 of bucket 8 with respect to arm 7 is α. This bucket-horizontal line angle θb represents an angle of bucket 8 with respect to the horizontal line.

Bucket-horizontal line angle θb is calculated by the following equation based on inclination angles θ1 to θ3.

θb=180°+θ1−θ2″θ3

When bucket-horizontal line angle θb is less than 90°, soil is more likely to be accumulated in bucket 8. When bucket-horizontal line angle θb is equal to or greater than 90°, soil is more likely to be ejected from bucket 8. When bucket-horizontal line angle θb is 180°, soil is completely ejected from bucket 8.

As bucket-horizontal line angle θb is greater, the posture of bucket 8 is more likely to be brought into the soil ejecting state.

In the present example, when bucket-horizontal line angle θb is equal to or greater than a prescribed angle, it is determined that the soil ejecting state occurs.

[Operation Process]

FIG. 8 is a diagram illustrating the operation process of work vehicle CM in the excavation operation according to the first modification of the embodiment.

As shown in FIG. 8, work implement controller 26 determines whether bucket 8 is operated or not (step S10). Specifically, work implement controller 26 determines whether or not first operation lever 25R is operated in the right-left direction.

When work implement controller 26 determines in step S10 that bucket 8 is operated (YES in step S10), it calculates the bucket angle (step S11).

Specifically, based on the detection result from bucket cylinder stroke sensor 18, work implement controller 26 calculates angle (bucket angle) θ3 of bucket 8 with respect to arm 7.

When work implement controller 26 determines in step S10 that bucket 8 is not operated (NO in step S10), the state in step S10 is maintained.

Then, work implement controller 26 calculates bucket-horizontal line angle θb (step S12).

Specifically, based on the method described with reference to FIG. 7, bucket-horizontal line angle θb formed between the horizontal line and the line segment that connects bucket pin 15 and cutting edge 8 a of bucket 8 is calculated. Inclination angles θ1 and θ2 are calculated based on the detection results from boom cylinder stroke sensor 16 and arm cylinder stroke sensor 17, respectively. When inclination angles θ1 and θ2 are calculated before the operation of bucket 8, these values can also be utilized.

Then, work implement controller 26 determines whether or not the calculated bucket-horizontal line angle θb is equal to or greater than a prescribed angle R (step S14). Prescribed angle R is equal to or greater than 90°.

When work implement controller 26 determines in step S14 that the calculated bucket-horizontal line angle θb is equal to or greater than prescribed angle R (YES in step S14), work implement controller 26 determines whether the operation of the bucket ends or not (step S16).

When work implement controller 26 determines in step S14 that the calculated bucket-horizontal line angle θb is less than prescribed angle R (NO in step S14), the process is returned to step S10.

When work implement controller 26 determines in step S16 that the operation of the bucket ends (YES in step S16), it adjusts bucket angle θ3 to bucket angle P (step S18). Work implement controller 26 drives direction control valve 64, through which the hydraulic oil to be supplied to bucket cylinder 12 flows, so as to set bucket angle θ3 to be bucket angle P.

Then, the process ends (end).

When only arm 7 is operated, work implement controller 26 adjusts bucket angle θ3 to bucket angle P such that the excavation angle formed between the excavation direction of cutting edge 8 a of bucket 8 and the direction of cutting edge 8 a of bucket 8 becomes equal to prescribed angle Q.

The posture of bucket 8 is adjusted before the start of excavation, that is, before the excavation operation is started. Automatic control is performed such that the excavation angle achieved by operating arm 7 for the posture of bucket 8 becomes an optimum angle. Thereby, the resistance (load) of soil against bucket 8 at the start of excavation is reduced. By adjusting the posture of bucket 8 before the start of excavation, a complicated computation does not have to be done during the excavation operation, so that an efficient excavation operation can be performed in a simple manner.

According to the command to operate bucket 8, work implement controller 26 calculates bucket-horizontal line angle θb as the angle of bucket 8 with respect to the horizontal line, and determines whether or not bucket-horizontal line angle θb is equal to or greater than prescribed angle R. When it is determined that bucket-horizontal line angle θb is equal to or greater than prescribed angle R, it is determined that the posture of bucket 8 is in the soil ejecting state. When work implement controller 26 determines that the soil ejecting state occurs, it adjusts the angle of bucket 8 to bucket angle P.

As a result, even when no instruction is given from the operator by pressing excavation button 25P, bucket 8 can be autonomously controlled to be set at a prescribed bucket angle before the start of excavation according to the command to operate bucket 8. Accordingly, the operation load onto the operator can be reduced, and also, an efficient excavation operation can be simply performed.

(Second Modification)

The work vehicle according to the second modification of the embodiment further determines the load onto work implement 2, and, when it determines that the soil ejecting state occurs, it autonomously adjusts the angle of bucket 8.

FIG. 9 is a functional block diagram illustrating the configuration of a control system 200A according to the second modification of the embodiment.

As shown in FIG. 9, control system 200A is different from control system 200 in that it further includes a load sensor 28, and that operation device 25 is replaced with an operation device 25#.

In the figure, operation device 25# has a configuration from which excavation button 25P is removed, as compared with operation device 25. Since other configurations are the same as those described with reference to FIG. 3, the detailed description thereof will not be repeated.

Load sensor 28 is attached to bucket 8.

According to load sensor 28 attached to bucket 8, work implement controller 26 determines whether work implement 2 has performed the soil ejecting operation or not.

The value of load sensor 28 is increased in accordance with the excavation operation in which bucket 8 excavates soil. The value of load sensor 28 is decreased in accordance with the soil ejecting operation in which bucket 8 ejects soil.

Work implement controller 26 determines whether or not the value of the load is equal to or greater than the first value in accordance with the detection result from load sensor 28. When the value of the load is equal to or greater than the first value, work implement controller 26 determines that the excavation operation has been performed.

After work implement controller 26 determines that the excavation operation has been performed, it determines whether or not the value of the load is less than the second value smaller than the first value in accordance with the detection result from load sensor 28.

When the value of the load is less than the second value in accordance with the detection result from load sensor 28, work implement controller 26 determines that the soil ejecting operation has been performed. The first value and the second value may also be the same value.

[Operation Process]

FIG. 10 is a diagram illustrating the operation process of work vehicle CM in the excavation operation according to the second modification of the embodiment.

As shown in FIG. 10, work implement controller 26 determines whether or not the load is relatively large according to the detection result from load sensor 28 (step S20). Specifically, work implement controller 26 determines whether or not the value is equal to or greater than the first value in accordance with the detection result from load sensor 28. Work implement controller 26 determines whether the excavation operation has been performed or not.

When work implement controller 26 determines in step S20 that the load is relatively large according to the detection result from load sensor 28 (YES in step S20), the process proceeds to step S22.

When work implement controller 26 determines in step S20 that the load is not relatively large according to the detection result from load sensor 28 (NO in step S20), the state in step S20 is maintained.

In step S22, work implement controller 26 determines whether bucket 8 is operated or not. Specifically, work implement controller 26 determines whether first operation lever 25R is operated in the right-left direction.

When work implement controller 26 determines in step S22 that bucket 8 is operated (YES in step S22), it then determines whether or not the load of the bucket is relatively small (step S24). Specifically, work implement controller 26 determines whether or not the value is less than the second value in accordance with the detection result from load sensor 28. Work implement controller 26 determines whether the soil ejecting operation has been performed or not.

When work implement controller 26 determines in step S22 that bucket 8 is not operated (NO in step S22), the state in step S22 is maintained.

When work implement controller 26 determines in step S24 that the load of bucket 8 is relatively small (YES in step S24), the bucket angle is calculated (step S11). Specifically, based on the detection result from bucket cylinder stroke sensor 18, work implement controller 26 calculates angle (bucket angle) θ3 of bucket 8 with respect to arm 7.

When work implement controller 26 determines in step S24 that the load is not relatively small according to the detection result from load sensor 28 (NO in step S24), the process is returned to step S22.

Then, work implement controller 26 calculates bucket-horizontal line angle θb (step S12). Since a series of processes in steps S11 to S18 is the same as those described with reference to FIG. 8, the detailed description thereof will not be repeated.

According to the detection result from load sensor 28, work implement controller 26 determines whether the soil ejecting operation has been performed or not. When work implement controller 26 determines that the soil ejecting operation has been performed, then, according to the command to operate bucket 8, it calculates bucket-horizontal line angle θb and determines whether or not bucket-horizontal line angle θb is equal to or greater than prescribed angle R. Thereby, it is determined whether the posture of bucket 8 is in the soil ejecting state or not. When the posture of bucket 8 is in the soil ejecting state, bucket angle θ3 is adjusted to bucket angle P.

Based on each of the detection result from load sensor 28 and the posture state of bucket 8, work implement controller 26 determines whether the soil ejecting operation has been performed or not.

Based on each of the detection result from load sensor 28 and the posture state of bucket 8, work implement controller 26 determines whether the soil ejecting operation has been performed or not. Accordingly, work implement controller 26 can reliably determine whether the soil ejecting operation has been performed or not. Then, before the start of excavation at which it was reliably determined that the soil ejecting operation has been performed, bucket angle θ3 is adjusted to bucket angle P.

As a result, work implement controller 26 determines with sufficient accuracy that the soil ejecting operation has already been performed and excavation is not yet started (before start of excavation). Thus, an efficient excavation operation can be performed in a simple manner.

Although the explanation has been given with regard to the configuration in which load sensor 28 is attached to bucket 8, the configuration of detecting a load by a sensor for measuring the hydraulic pressure inside the hydraulic cylinder may be employed. For example, the hydraulic pressure of the hydraulic oil supplied to bucket cylinder 12 is measured by a sensor, so that it can be determined whether the load applied onto bucket 8 is relatively large or small.

Other Embodiments

FIG. 11 is a functional block diagram illustrating the configuration of a control system 200B configured to control a work vehicle according to another embodiment.

As shown in FIG. 11, control system 200B is different from control system 200A in that a receiver 29 is provided in place of load sensor 28. Since other configurations are the same as those described with reference to FIG. 9, the detailed description thereof will not be repeated.

Receiver 29 outputs the received command to work implement controller 26.

Receiver 29 receives an excavation start command transmitted from outside, and outputs the received command to work implement controller 26.

In response to the excavation start command received in receiver 29, work implement controller 26 calculates the angle of bucket 8 with respect to arm 7, and controls the work implement such that the calculated angle becomes equal to a prescribed angle.

Specifically, the above-described operation process is performed upon reception of the excavation start command in place of reception of the input by excavation button 25P that has been described with reference to FIG. 6.

In the manner similar to that described above, the posture of bucket 8 is adjusted before the start of excavation, that is, before the excavation operation is started. Automatic control is performed such that the excavation angle achieved by operating arm 7 for the posture of bucket 8 becomes an optimum angle. Thereby, the resistance (load) of soil against bucket 8 at the start of excavation is reduced. By adjusting the posture of bucket 8 before the start of excavation, a complicated computation does not have to be done during the excavation operation, so that an efficient excavation operation can be performed in a simple manner.

An efficient excavation operation can be performed according to the operation start command from outside.

FIG. 12 is a diagram illustrating a concept of a work vehicle system according to another embodiment.

As shown in FIG. 12, the work vehicle system according to another embodiment configures a control system for controlling work vehicle CM from an external base station 300. Specifically, the functions of work implement controller 26 and operation device 25 that have been described with reference to FIG. 3 are provided in external base station 300 and the like.

Base station 300 includes: a work implement controller 26# having the same function as that of work implement controller 26, and an operation device 25# having the same function as that of operation device 25.

Work implement controller 26# receives the operation command of operation device 25#, and outputs a motion command for controlling work vehicle CM. Work vehicle CM operates according to the motion command from work implement controller 26#. Specifically, work implement controller 26# outputs the motion command for driving direction control valve 64 that has been described with reference to FIG. 3. Work implement controller 26# receives the input of the sensor information from each of boom cylinder stroke sensor 16, arm cylinder stroke sensor 17, and bucket cylinder stroke sensor 18.

According to the above-described configuration, the operation process of the excavation operation according to the embodiment that has been described with reference to FIG. 6 can be performed by work implement controller 26#.

As a result, when a work vehicle is controlled from base station 300 that is remotely located, the configuration according to the embodiment can be applied. Thus, an efficient excavation operation can be performed in a simple manner.

Although the explanation has been given with regard to the configuration in which an operator controls work vehicle CM according to the input of the operation by the operation lever as an operation device, the present invention is also applicable to the configuration in which work vehicle CM is autonomously controlled without providing an operation device. For example, the present invention is also applicable to the case where an operation command for the excavation operation is programmed in advance, and the work implement controller is operated according to the programmed operation command. Specifically, in the case where an autonomous control program for autonomously controlling work vehicle CM is started according to the instruction from the user, and the work implement controller starts the excavation operation according to the programmed operation command, the following process may be included, in which the angle of bucket 8 with respect to arm 7 is calculated, and the work implement is operated such that the calculated angle becomes equal to a prescribed angle.

The explanation has been given with regard to the case of using, as an excavation angle, prescribed angle Q at which the resistance of soil shows a minimum value. However, the invention is not limited thereto, and work implement 2 may be controlled based on an optional prescribed angle as an excavation angle. The value of the excavation angle is also not limited to a fixed value. For example, the value of prescribed angle Q may be changed in accordance with the soil property.

<Functions and Effects>

The functions and effects of the above-described embodiment will be hereinafter described.

Work vehicle CM in the embodiment includes vehicular body 1 and work implement 2 as shown in FIG. 1. Work implement 2 includes boom 6 pivotable with respect to vehicular body 1, arm 7 pivotable with respect to boom 6, and bucket 8 pivotable with respect to arm 7. Work vehicle CM is provided with work implement controller 26 as shown in FIG. 3. Work implement controller 26 calculates the angle of bucket 8 with respect to arm 7 according to the input (excavation command) by excavation button 25P before the start of excavation, and controls bucket 8 such that the calculated angle becomes equal to bucket angle P.

Work vehicle CM in the embodiment controls bucket 8 to be set at bucket angle P before the start of excavation. Accordingly, the excavation operation of work implement 2 is performed at the excavation angle of prescribed angle Q at which the resistance of soil shows a minimum value, as shown in FIG. 4. As a result, by adjusting the posture of bucket 8 before the start of excavation, a complicated computation does not have to be done during the excavation operation, so that an efficient excavation operation can be performed in a simple manner.

Work vehicle CM in the embodiment is provided with work implement controller 26 configured to determine whether the soil ejecting operation as shown in FIG. 7 has been performed or not according to the operation command. When work implement controller 26 determines that the soil ejecting operation has been performed, it calculates the angle of bucket 8 with respect to arm 7, and controls bucket 8 such that the calculated angle becomes equal to bucket angle P.

Work vehicle CM in the embodiment determines whether the soil ejecting operation of bucket 8 has been performed or not, and controls bucket 8 to be set at bucket angle P before the start of excavation. Accordingly, when the soil ejecting operation of bucket 8 has been performed, the preparations before the start of excavation are made. Thus, an efficient excavation operation can be performed in a simple manner.

Work implement controller 26 of work vehicle CM in the embodiment calculates a bucket-horizontal line angle. Bucket-horizontal line angle θb represents an angle formed between the horizontal line and the line segment that connects bucket pin 15 and cutting edge 8 a of bucket 8. When bucket-horizontal line angle θb is equal to or greater than prescribed angle R, bucket 8 is controlled such that the calculated angle becomes equal to bucket angle P.

When the bucket-horizontal line angle is equal to or greater than prescribed angle R as shown in FIG. 7, work vehicle CM in the embodiment determines that the posture of bucket 8 is in the soil ejecting state, and controls bucket 8 to be set at bucket angle P before the start of excavation. Accordingly, after it is determined based on the posture of bucket 8 whether the soil ejecting state occurs or not, the preparations before the start of excavation are made. Thus, it becomes possible to readily recognize that the soil ejecting state occurs. Also, an efficient excavation operation can be performed in a simple manner.

Work vehicle CM in the embodiment is provided with load sensor 28 for detecting the load applied to bucket 8. Work implement controller 26 calculates the angle of bucket 8 with respect to arm 7 based on the operation command of first operation lever 25R before the start of excavation and the detection result from load sensor 28 during excavation. Then, work implement controller 26 controls bucket 8 such that the calculated angle becomes equal to bucket angle P.

Based on the detection result from load sensor 28, work vehicle CM in the embodiment determines whether the soil ejecting operation has been performed or not. Then, when work vehicle CM in the embodiment determines that soil ejecting operation has been performed, it controls bucket 8 to be set at bucket angle P before the start of excavation. Thus, after it is determined based on the detection result from the load sensor whether the soil ejecting state occurs or not, the preparations before the start of excavation are made. Accordingly, it becomes possible to accurately recognize that the soil ejecting state occurs. Also, an efficient excavation operation can be performed in a simple manner.

Work vehicle CM in the embodiment is provided with receiver 29 configured to receive an operation start command as shown in FIG. 11. According to the excavation start command received in receiver 29 before the start of excavation, work implement controller 26 calculates the angle of bucket 8 with respect to arm 7, and controls bucket 8 such that the calculated angle becomes equal to bucket angle P.

According to the operation start command from outside, work vehicle CM in the embodiment controls bucket 8 to be set at bucket angle P before the start of excavation. Thus, by remote control from outside, an efficient excavation operation can be performed in a simple manner.

As shown in FIG. 1, work vehicle CM in the embodiment is provided with bucket cylinder 12 configured to drive bucket 8 according to the operation command before the start of excavation. Work implement controller 26 calculates the angle of bucket 8 with respect to arm 7 based on the stroke length of bucket cylinder 12, and controls bucket 8 such that the calculated angle becomes equal to bucket angle P.

Work vehicle CM in the embodiment can calculate the angle of bucket 8 with respect to arm 7 based on the stroke length of bucket cylinder 12. This eliminates the need to provide a detector for detecting the angle of bucket 8, so that an efficient excavation operation can be performed in a simple manner.

Work vehicle CM in the embodiment is provided with vehicular body 1 and work implement 2 as shown in FIG. 1. Work implement 2 includes boom 6 pivotable with respect to vehicular body 1, arm 7 pivotable with respect to boom 6, and bucket 8 pivotable with respect to arm 7. In the method of controlling work vehicle CM, the following steps are performed, which include: receiving an operation command before start of excavation; calculating an angle of bucket 8 with respect to arm 7 according to the operation command; and controlling bucket 8 such that the calculated angle becomes equal to bucket angle P.

In the method of controlling work vehicle CM in the embodiment, bucket 8 is controlled to be set at bucket angle P before the start of excavation. Thus, the excavation operation of work implement 2 is performed at the excavation angle of prescribed angle Q at which the resistance of soil shows a minimum value, as shown in

FIG. 4. As a result, by adjusting the posture of bucket 8 before the start of excavation, a complicated computation does not have to be done during the excavation operation, so that an efficient excavation operation can be performed in a simple manner.

A hydraulic excavator has been described above as an example of a work vehicle, but the present invention is applicable also to a work vehicle such as a bulldozer and a wheel loader.

Although the embodiments of the present disclosure have been described as above, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present disclosure is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the meaning and scope equivalent to the terms of the claims.

REFERENCE SIGNS LIST

1 vehicular body, 2 work implement, 3 revolving unit, 4 operator's cab, 4S operator's seat, 5 traveling unit, 5Cr crawler belt, 6 boom, 7 arm, 8 bucket, 8 a cutting edge, 9 engine compartment, 10 boom cylinder, 11 arm cylinder, 12 bucket cylinder, 13 boom pin, 14 arm pin, 15 bucket pin, 16 boom cylinder stroke sensor, 17 arm cylinder stroke sensor, 18 bucket cylinder stroke sensor, 19 handrail, 25, 25# operation device, 25L second operation lever, 25P excavation button, 25R first operation lever, 26, 26# work implement controller, 28 load sensor, 29 receiver, 60 hydraulic cylinder, 64 direction control valve, 66 pressure sensor, 200, 200A, 200B control system, 300 base station. 

1. A work vehicle comprising: a vehicular body; a work implement including a boom pivotable with respect to the vehicular body, an arm pivotable with respect to the boom, and a bucket pivotable with respect to the arm; and a controller configured to calculate an angle of the bucket with respect to the arm according to an operation command before start of excavation, and control the bucket such that the calculated angle becomes equal to a first angle.
 2. The work vehicle according to claim 1, wherein the controller is configured to determine whether or not a soil ejecting operation is performed according to the operation command, when it is determined that the soil ejecting operation is performed, calculate the angle of the bucket with respect to the arm, and control the bucket such that the calculated angle becomes equal to the first angle.
 3. The work vehicle according to claim 1, wherein the controller is configured to calculate a bucket-horizontal line angle formed between a horizontal line and a line segment that connects a bucket pin as a center of rotation of the bucket and a cutting edge of the bucket, and when the bucket-horizontal line angle is equal to or greater than a second angle, control the bucket such that the calculated angle of the bucket with respect to the arm becomes equal to the first angle.
 4. The work vehicle according to claim 1, further comprising a load detection unit configured to detect a load applied to the work implement, wherein the controller is configured to calculate the angle of the bucket with respect to the arm according to the operation command before start of excavation and a detection result from the load detection unit during excavation, and control the bucket such that the calculated angle becomes equal to the first angle.
 5. The work vehicle according to claim 1, further comprising a receiver configured to receive the operation command, wherein the controller is configured to calculate the angle of the bucket with respect to the arm according to the operation command before start of excavation, the operation command being received in the receiver before start of excavation, and control the bucket such that the calculated angle becomes equal to the first angle.
 6. The work vehicle according to claim 1, further comprising a bucket cylinder configured to drive the bucket according to the operation command before start of excavation, wherein the controller is configured to calculate the angle of the bucket with respect to the arm based on a stroke length of the bucket cylinder, and control the bucket such that the calculated angle becomes equal to the first angle.
 7. A method of controlling a work vehicle including a work implement that includes a boom pivotable with respect to a vehicular body, an arm pivotable with respect to the boom, and a bucket pivotable with respect to the arm, the method comprising: receiving an operation command before start of excavation; calculating an angle of the bucket with respect to the arm according to the operation command; and controlling the bucket such that the calculated angle becomes equal to a first angle. 